1. Field of the Invention
This invention relates to the testing and treatment of oil and gas wells, and in particular, to the testing and treatment of such wells with production tubing in place
2. Description of Related Art
Testing is necessary to evaluate a well. Production testing occurs at various stages in the life of a well. For example, drill stem testing can be performed in an open hole before casing is set to establish the contribution from each identified potential producing zone.
A single subsurface formation can be tested in an open hole for production potential before casing has been set or the well has been completed. In some wells, multiple subsurface formations will be tested for production potential. If the well is deemed to have production potential, the open hole will be cased and the casing will be perforated at the subsurface formations that have tested favorably for hydrocarbon production.
One approach to production testing is disclosed in U.S. Pat. No. 6,543,540. The '540 patent discloses a method for performing production testing in open holes and in cased holes that avoids transporting formation fluid to the surface. Formation fluid is conducted from a first, expected permeable formation to a second permeable formation, as opposed to prior art techniques where fluid is conducted between a formation and the surface.
After a well has been cased, it must be perforated. Wells are often tested again after perforation, but before production tubing has been set. U.S. Pat. No. 6,543,538 discloses a method for perforating and treating multiple wellbore intervals before production tubing has been installed. One embodiment involves perforating at least one interval of the one or more subterranean formations penetrated by a given wellbore, pumping the desired treatment fluid without removing the perforating device from the wellbore, deploying some item or substance in the wellbore to removably block further fluid flow into the treated perforations, and then repeating the process for at least one more interval of subterranean formation. Another embodiment involves perforating at least one interval of the one or more subterranean formations penetrated by a given wellbore, pumping the desired treatment fluid without removing the perforating device from the wellbore, actuating a mechanical diversion device in the wellbore to removably block further fluid flow into the treated perforations, and repeating the process for at least one more interval of subterranean formation.
Another method for testing a cased well without production tubing is disclosed in U.S. Pat. No. 6,527,052. In this disclosure, drill pipe or coiled tubing is connected to a formation test assembly for testing a cased well. In one embodiment, the test is performed downhole without flowing fluids to the earth's surface. In another embodiment, a formation is perforated and fluids from the formation are flowed into a large surge chamber associated with a tubular string installed in the well. In another embodiment, fluids from a first formation are flowed into a tubular string installed in the well, and the fluids are then disposed of by injecting the fluids into a second formation. In yet another embodiment, fluids are flowed from a first formation and into a second formation utilizing an apparatus which may be conveyed into a tubular string positioned in the well.
If the well still appears viable after casing and perforation, production tubing will be set to complete the well, or additional perforating may occur. Drill stem testing procedures are not suitable on a completed well with production tubing in place because the drill pipe and equipment often used in drill stem testing will not fit in the production tubing. Further, conventional flow testing equipment cannot be run in production tubing even if the equipment is run on a wire line or a slick line.
After a well has been in production, the production rate may decline over time for a number of different reasons. It may therefore be necessary and desirable to test one or more subsurface production zones to better evaluate the reasons for the decline in production. Conventional tests on completed wells with production tubing in place are typically less comprehensive than drill stem tests in the open hole or a cased hole. The other option is to remove the production tubing for a conventional drill stem test. This latter approach is expensive. There is therefore a need to be able to run separate tests of each production zone in a completed well with production tubing in place.
One solution is disclosed in U.S. Pat. No. 5,353,875. In the '875 Patent, testing may be accomplished without removing the production tubing string from the well. The production of the well is shut down and then a coiled tubing test string is run down into the production tubing string. The coiled tubing test string includes a conveyance coiled tubing string, a tester valve carried by the conveyance coiled tubing string, and a test packer carried by the conveyance coiled tubing string. The test packer is set within one of the casing bore and the production tubing bore above perforations which communicate the casing bore with a subsurface formation. Drawdown and buildup testing of the subsurface formation can then be accomplished by opening and closing the tester valve to selectively flow well fluid up through the conveyance coiled tubing string or shut in the conveyance coiled tubing string. After the drawdown/buildup testing is completed, the coiled tubing test string is removed from the well and production of the well is resumed up through the production tubing bore. The problem with the method of the '875 patent is that hydrocarbons flow to the surface through the coiled tubing. Use of this flowpath is typically not a favored procedure in the field. Therefore, there is still a need for a method and apparatus that will facilitate testing of one production zone at a time in a completed well with production tubing in place.
If the testing procedures indicate that there is a problem, it is often preferable to stimulate or otherwise treat an existing well to improve production rates, rather than drill a new well. There are a number of ways to treat a completed well with multiple production zones, including matrix acidizing. In the past, it has been common to treat all production zones at one time. The problem with this prior art technique is that large amounts of acid are pumped into the well. After the acid is returned to the surface, it must be disposed. Further, treatment of all production zones may not have been necessary because only one production zone may have had a problem. Therefore, there is a need for a method and apparatus that will facilitate treatment of one production zone at a time in a completed well with production tubing in place.
One technique that has been suggested for treatment of one production zone at a time in a completed well with production tubing in place is described in U.S. Pat. No. 5,350,018. This technique uses inflatable packers to isolate a production zone. Treatment fluid is pumped down the coiled tubing to the zone and the treatment fluid and hydrocarbons flow back up the coiled tubing after the treatment. Again, it is desirable to avoid flowing hydrocarbons up the coiled tubing to the surface. There is still a need for a method and apparatus that avoids return flow through the coiled tubing. (See also U.S. Pat. No. 4,913,231).
A downhole stripper is used in the present invention. This downhole stripper is an existing electric submersible pump (ESP) bypass logging plug already available but not used in the same way as the present invention. Both PCE and Phoenix Petroleum Services market this logging plug.
An annular control tubing injection valve, sometimes referred to as an ACTIV, is also used in the present invention. Prior art exists on annular communication tools, such as a pick-up unloader used in packer operations marketed by Petro Tech Tools, a division of Schlumberger, as Product No. 3544. The pick-up unloader is tension and compression-activated. The pick-up unloader is a simple version of an ACTIV. Schlumberger pressure pulse technology (IRIS) may also be used to open and close the ACTIV.